Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

It is still possible to trigger a slab avalanche within wind-drifted snow at upper elevations. Look for actively drifting snow, fresh sharp cornices, or rounded pillows once you ascend above the breakable crust. Steer around steep wind-loaded features and dial back your ambitions if you encounter propagating cracks or whumphs.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    You can trigger a small slab within freshly drifted snow and there's a lingering risk of triggering a large slab formed by SW winds and over 1 ft of snow during Sunday's storm. Winds will be just strong enough to transport snow near ridgelines Tuesday night through Wednesday. Slabs within the fresh or recently transported snow will be fairly easy to trigger. Active wind deposition or fresh, sharp cornices can help you key into specific features to steer around. Given the larger potential size of older slabs, they deserve your attention. Bulges in the slope may indicate either wind deposition or a convex rollover where you are most likely to trigger an avalanche.  Pay attention to notable signs of instability, including propagating cracks and whumphs as you travel; and check for any signs of a poor bond with the stout 12/7 crust around 16" or so below the snow surface.

    On Saturday, observers found the snow above the 12/7 crust had an upside-down density profile but generally bonds well to the 12/7. Wind drifting or the potential for areas of surface hoar contribute the necessary ingredients for an avalanche down to the 12/7 crust. Thus it's worth jumping on a few low-consequence test slopes and digging down to the 12/7 interface to check the bond interfaces before entering consequential terrain.

    (12/12/2023)

    A small cornice near Blue Lake Peak. At upper elevations, you'll find dry snow that may be easily transported by the wind on Thursday. 

    Photo: Matt Primomo

Avalanche Discussion

While the likelihood of triggering a slide is decreasing, it's also always a good idea to step into new terrain slowly. Don't commit to larger slopes before first seeing how the snow reacts on many small, lower-consequence slopes. We only have limited observations from the zone, and higher elevations warrant further investigation. 

Expect a strong inversion once again on Wednesday. Upper elevations could rise above the freezing mark and minor loose activity can be expected on sun-drenched slopes.

During the past two days, observers traveling on both sides of Highway 20 have found a thin 12/10 zipper crust extending up to 6300-6500 ft. This crust formed near the end of a storm system that brought over a foot of snow to Washington Pass.  In areas closer to Silverstar and Delancey Ridges the crust is very thin and brittle and may do less to limit the potential for avalanches in eastern portions of the zone. On Tuesday, near Spire Gulley and Blue Lake Peak, observers found cracking within Sunday's storm snow while approaching ridgelines. A slightly wind-stiffened slab sits above gradually decreasing snow density down to the 12/7 crust  16" below the snow surface. They also found a good bond to the crust in that location. Winds were sifting snow over the skin tracks at these upper locations and adding to the near-surface slab. They also found a zipper crust on due S aspects, but good powder for riding on all other aspects.

Sunday was a warm and steamy day for the entire region, and observers reported hearing and seeing natural avalanches as light rain and warm temperatures affected the fresh storm snow. The majority of the avalanches we have information on were in the small to medium range, and were mostly loose, but some slabs were identified. Check out Will's great ob and photos here.

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